JPH06101446B2 - Plasma processing method and plasma processing apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and a plasma processing apparatus for forming a film on a semiconductor wafer or etching a semiconductor wafer in a semiconductor device manufacturing process. .

[Conventional technology]

Conventionally, this type of plasma treatment is usually performed by attaching a semiconductor wafer (hereinafter, simply referred to as a wafer) to an electrode in a chamber which is a reaction container and generating plasma in the chamber. It is performed while cooling from the back side by the electrodes. This will be described with reference to FIG.

FIG. 2 is a sectional view showing a conventional plasma processing apparatus of this type. In the figure, reference numeral 1 denotes a chamber as a reaction container. In this chamber 1, a wafer passage 1a for loading and unloading a wafer 2 to be processed into and out of the chamber 1 is opened at a side portion, and a reaction is provided at a ceiling portion thereof. A gas introduction pipe 1b for supplying gas is connected, and an exhaust pipe 1c for communicating with a vacuum pump (not shown) or the like for reducing the pressure in the chamber 1 to a predetermined pressure is connected to the bottom. There is.
Further, in this chamber 1, the wafer passage 1a has a shutter 3
It is configured to be selectively opened and closed by, and the inside of the chamber 1 is hermetically closed in a high vacuum state with the shutter 3 closed. Reference numeral 4 is a lower electrode as a sample table on which the wafer 2 is mounted, 5 is an upper electrode, and both electrodes 4 and 5 are horizontally installed in the chamber 1 with their main surfaces facing each other. The lower electrode 4 has a recess 6 opened at the wafer mounting portion on the electrode surface side, and has a cooling gas introduction pipe 7a at the lower part thereof via communication passages 4a, 4b opened at the bottom of the recess 6. Then, the cooling gas exhaust pipe 7b is connected. The cooling gas supply pipe 7a is connected to a cooling gas supply device (not shown), and the cooling gas exhaust pipe 7b is connected to the chamber 1
Is connected to the exhaust pipe 1c. That is, when the wafer 2 is mounted on the lower electrode 4, the opening of the recess 6 is closed by the wafer 2 to form a cooling chamber in the recess 6, and the cooling gas introduction pipe 7a to the cooling gas exhaust pipe 7b are formed.
A cooling gas passage leading to the wafer 2 is formed, and the wafer 2 is cooled from the back side by the cooling gas flowing in the recess 6. An inert gas such as helium gas is used as the cooling gas. The upper electrode 5 is connected to a high frequency power source 8. Reference numeral 9 denotes a transfer arm for loading / unloading the wafer 2 into / from the chamber 1. The transfer arm 9 is configured so that the wafer 2 can be placed on or removed from the lower electrode 4.

Next, the operation of the conventional plasma processing apparatus configured as described above will be described. In order to perform plasma processing on the wafer 2 by this plasma processing apparatus, first, the wafer 2 is placed on the lower electrode 4 by the transfer arm 9 and the shutter 3 is closed. Next, the pressure inside the chamber 1 is reduced to a predetermined pressure, and a reaction gas is introduced into the chamber 1.
Supplied from 1b. Thereafter, high frequency power is applied between the upper electrode 5 and the lower electrode 4. The reaction gas is turned into plasma by the discharge between the electrodes 4 and 5, whereby the surface of the wafer 2 is processed. On the other hand, in parallel with this plasma processing, the wafer 2 is also cooled. In order to cool the wafer 2, the cooling gas is supplied to the cooling gas introduction pipe 7a, and the communication passage 4a of the lower electrode 4, the recess 6, the communication passage 4b and the cooling gas exhaust pipe 7b.
Through the exhaust pipe 1b. The cooling gas exchanges heat with the back surface of the wafer 2 when the cooling gas is caused to flow into the cooling chamber in the recess 6, so that the wafer 2 is cooled. After the plasma processing is completed, the shutter 3 is opened, the wafer 2 is taken out of the chamber 1 by the transfer arm 9, and the plasma processing step is completed.

[Problems to be Solved by the Invention]

However, in the conventional plasma processing apparatus configured as described above, a sensor for detecting whether or not the wafer 2 is mounted in the chamber 1 for high vacuum, reactive plasma gas, reaction products, etc. is provided. I can't. Therefore, there is a problem that the wafer 2 is mounted on the lower electrode 4 even though the wafer 2 is already mounted on the lower electrode 4. In such a case, the wafer 2 is stacked on the lower electrode 4.

[Means for Solving the Problems]

The plasma processing method according to the present invention supplies a cooling gas before mounting a wafer on an electrode, and detects whether or not a wafer is mounted by the pressure on the cooling gas passage downstream of the wafer cooling unit. Further, in the plasma processing apparatus according to the present invention, a pressure detector for detecting a pressure change depending on whether or not the wafer is attached to the electrode is arranged downstream of the wafer cooling unit in the cooling gas passage.

[Work]

When the wafer is not mounted on the wafer mounting electrode, the cooling gas leaks from the recess of the electrode into the reaction vessel. Therefore, the pressure downstream of the wafer cooling section in the cooling gas passage is when the wafer is mounted. Will be reduced compared to. According to the present invention, it is possible to detect the mounting / non-mounting of the wafer by supplying the cooling gas before the mounting operation of the wafer and measuring the pressure of the cooling gas passage on the downstream side of the wafer cooling unit.

〔Example〕

An embodiment of a plasma processing apparatus for carrying out the plasma processing method of the present invention will be described in detail below with reference to FIG.

FIG. 1 is a sectional view showing a plasma processing apparatus according to the present invention. In the figure, the same or similar members as those described in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted here. In FIG. 1, 11 is a vacuum gauge which is a pressure detector for detecting whether or not the wafer 2 is mounted on the lower electrode 4. The vacuum gauge 11 is connected to the cooling gas exhaust pipe 7b. The pressure change of the cooling gas flowing in the cooling gas passage can be measured.

Next, a procedure for detecting whether or not the wafer 2 is mounted by the vacuum gauge 11 described above will be described. When the wafer 2 is not mounted on the lower electrode 4, the cooling gas supplied from the cooling gas introducing pipe 7a into the recess 6 of the lower electrode 4 is because the recess 6 is not blocked by the wafer 2. It is diffused in the chamber 1. Therefore, the cooling gas exhaust pipe 7b
The pressure of the cooling gas flown into the chamber 1 decreases, and the degree of vacuum in the chamber 1 and the degree of vacuum indicated by the vacuum gauge 11 become substantially the same. When the wafer 2 is mounted on the lower electrode 4,
The cooling gas is supplied to the cooling chamber formed by the recess 6 of the lower electrode 4 and the wafer 2, and is flown into the cooling gas exhaust pipe 7b. At this time, the degree of vacuum indicated by the vacuum gauge 11 temporarily becomes higher than that in the chamber 1. That is, whether or not the wafer 2 is mounted can be detected by the value indicated by the vacuum gauge 11, and when the value indicated by the vacuum gauge 11 is substantially the same as the vacuum degree in the chamber 1, the wafer 2 is not attached. It is possible to detect that the wafer 2 is mounted, and it is possible to detect that the wafer 2 is mounted when the degree of vacuum in the chamber 1 is higher.

As described above, in order to perform the plasma processing on the wafer 2 by the plasma processing apparatus having the vacuum gauge 11, first, the cooling gas is supplied to the lower electrode 4 before mounting the new wafer 2 in the chamber 1. Make sure that 2 is not left on the bottom electrode 4. The confirmation of the residual wafer is performed by the vacuum gauge 11 as described above. When the value indicated by the vacuum gauge 11 is higher than that in the chamber 1, first, the wafer 2 left on the lower electrode 4 is transferred to the outside of the chamber 1 by the transfer arm 9, and a new wafer 2 is moved downward. It is placed on the electrode 4. When the value indicated by the vacuum gauge is substantially the same as that in the chamber 1, the wafer 2 is not mounted yet, so that a new wafer 2 is placed on the lower electrode 4 by the transfer arm 9. By thus confirming whether or not the wafer 2 is mounted on the lower electrode 4 and then performing the mounting operation of the wafer 2, it is possible to prevent the wafer 2 from being erroneously stacked on the lower electrode 4. Thereafter, the shutter 3 is closed, the pressure inside the chamber 1 is reduced to a predetermined pressure, and the reaction gas is supplied into the chamber 1 through the gas introduction pipe 1b. Then, high frequency power is applied to the upper electrode 5 and the lower electrode 4.
Apply between. The reaction gas is turned into plasma by the discharge between the electrodes 4 and 5, whereby the surface of the wafer 2 is processed. On the other hand, the wafer 2 is cooled in parallel with this plasma processing. The cooling gas sent from the cooling gas introduction pipe 7a into the recess 6 through the communication passage 4a contacts the back surface of the wafer 2 in the cooling chamber formed in the recess 6 to cool the wafer 2, and then the communication passage 4b. Then, it is exhausted by the exhaust pipe 1c through the cooling gas exhaust pipe 7b. After the plasma processing is completed, the shutter 3 is opened and the wafer 2 is taken out of the chamber 1 by the transfer arm 9 to complete the plasma processing step.

In this embodiment, the inside of the cooling gas exhaust pipe 7b and the chamber 1 are
Although the example of measuring the difference in the degree of vacuum with the inside is shown, the present invention is not limited to such a limitation, and if the pressure change in the cooling gas exhaust pipe 7b can be detected, the pressure is anywhere. You may compare. Further, in the present embodiment, an example in which the vacuum gauge 11 is used as the pressure detector has been shown, but other than the vacuum gauge can be used as long as it can detect the pressure change in the cooling gas exhaust pipe 7b. Good.

〔The invention's effect〕

As described above, the plasma processing method according to the present invention is
A cooling gas is supplied before mounting the wafer on the electrode, and the presence or absence of the mounting of the wafer is detected by the pressure on the cooling gas passage downstream of the wafer cooling unit. Since a pressure detector for detecting a pressure change depending on whether or not the wafer is attached to the electrode is arranged on the downstream side of the wafer cooling unit in the gas passage, it is possible to detect the pressure change when the wafer is not attached to the wafer attachment electrode. Since the cooling gas leaks from the concave portion of the electrode into the reaction container, the pressure in the cooling gas passage downstream of the wafer cooling unit is reduced as compared with the case where the wafer is mounted. It is possible to confirm whether the wafer is mounted or not by detecting the. Therefore, according to the present invention, it is possible to detect the mounting / non-mounting of the wafer before the mounting operation of the wafer. Therefore, it is possible to reliably prevent the wafers from being stacked on the wafer mounting electrode, and the product yield can be improved. The effect is that it can be improved. Further, in the plasma processing apparatus of the present invention, since the pressure detector is arranged outside the reaction vessel, it is not affected by high vacuum, reactive plasma gas, reaction products, etc. It can be implemented at low cost without the need to use special ones.

[Brief description of drawings]

FIG. 1 is a sectional view showing a plasma processing apparatus according to the present invention,
FIG. 2 is a sectional view showing a conventional plasma processing apparatus. 1 ... Chamber, 2 ... Wafer, 4 ... Lower electrode, 5 ...
… Upper electrode, 6 …… Recess, 7a …… Cooling gas inlet pipe, 7b ……
Cooling gas exhaust pipe, 11 ... Vacuum gauge.

Claims (2)

[Claims] 1. A recess in which an opening is closed by a wafer,
In a plasma processing method of cooling a wafer from the backside during plasma processing by a wafer mounting electrode having a cooling gas passage communicated with the recess, the cooling gas is supplied before the wafer is mounted on the electrode. In the plasma processing method, the presence / absence of wafer mounting is detected by the pressure on the downstream side of the wafer cooling unit in. 2. A wafer mounting electrode in a reaction vessel is provided with a recess whose opening is closed by the wafer, and a cooling gas passage communicating with the recess, and the wafer is cooled from the back side by the cooling gas. In the plasma processing device,
Downstream of the wafer cooling unit in the cooling gas passage,
A plasma processing apparatus comprising a pressure detector for detecting a pressure change depending on whether or not a wafer is attached to an electrode.